Wafer and method of producing a substrate by transfer of a layer that includes foreign species

ABSTRACT

A method of producing a substrate that has a transfer crystalline layer transferred from a donor wafer onto a support. The transfer layer can include one or more foreign species to modify its properties. In the preferred embodiment an atomic species is implanted into a zone of the donor wafer that is substantially free of foreign species to form an embrittlement or weakened zone below a bonding face thereof, with the weakened zone and the bonding face delimiting a transfer layer to be transferred. The donor wafer is preferably then bonded at the level of its bonding face to a support. Stresses are then preferably applied to produce a cleavage in the region of the weakened zone to obtain a substrate that includes the support and the transfer layer. Foreign species are preferably diffused into the thickness of the transfer layer prior to implantation or after cleavage to modify the properties of the transfer layer, preferably its electrical or optical properties. The preferred embodiment produces substrates with a thin InP layer rendered semi-insulating by iron diffusion.

FIELD OF THE INVENTION

[0001] The present invention generally relates to methods of fabricatingsubstrates by stacking and transfer of thin transfer layers ofsemiconductor materials, and is preferably applicable to monocrystallinelayers.

BACKGROUND OF THE INVENTION

[0002] A method known as SMART-CUTE®, based on implanting atomic speciessuch as hydrogen and/or rare gases and molecular bonding, allows thinfilms to be produced and assembled on supports. More precisely,implanting atomic species creates a weakened zone and embrittlement in alayer at a depth at which the film is to be detached from a donor wafer.A support or stiffener is attached thereto by molecular bonding. Theimplanted layer is then transferred by carrying out a treatment, such asa heat or mechanical treatment, to produce cleavage at the weakened zoneto detach the transfer layer. The thickness of the thin transfer film isselected in each case, but in general is on the order of a few hundredsor tens of nanometers. The surface obtained can then be polished such asby using a chemical or a mechanical-chemical method. Such a method canproduce heterostructures that cannot be obtained by epitaxy alone.

[0003] When heat treatments are carried out, such as to facilitatefracture or strengthen the bonding interface, these are conducted at alower temperature than during epitaxy, and inter-diffusion phenomena canbe advantageously reduced. This method also allows the remaining portionof the donor wafer left behind after fracturing or detaching, known asthe negative, to be recycled, and this is economically beneficial.

[0004] In industrial application, the production of a silicon oninsulator (SOI) substrate composed of a thin film of monocrystallinesilicon electrically insulated from a bulk substrate. In general, thebulk substrate is silicon, and the insulating silicon layer is amorphoussilica.

[0005] The method is also applicable to a wide range of materials,whether they form the implanted layer (SiC, GaAs, InP, LiNbO₃, etc.),the support or stiffener (monocrystalline or polycrystalline silicon,gallium arsenide, polycrystalline indium phosphide, quartz, etc.), orany bonding layer (SiO₂, Si₃N₄, Pd, etc.).

[0006] It is also possible to use the method to produce“partial-substrates” intended to receive an additional layer byepitaxial growth on the transferred thin layer. This can provide severaladvantages:

[0007] size: since some substrates are not available in standardindustrial sizes, it is thus possible to carry out a method oftransferring a thin layer onto a support or stiffener with a largerdiameter. In particular, a 4 inch diameter InP film can be transferredonto a 6 inch diameter support so as to remain compatible with 6 inchstandard micro-electronics fabrication facilities;

[0008] brittleness: the brittleness of certain bulk substrates (forexample InP) can cause the substrates and components to break duringfabrication and manipulation and may thereby significantly increaseproduction costs. The layer transfer method can advantageously beemployed if a stiffener can provide strength to the structure (forexample, a thin InP layer on an Si or GaAs support):

[0009] cost: the high cost of certain substrates may justify using alayer transfer method to transfer a very thin layer (a few tens ofnanometers thick) onto a cheap stiffening substrate; the operation beingrepeated after recycling the donor wafer (negative);

[0010] compliant effect: this term represents a certain adaptability ofthe transfer layer, particularly as regards dimensions. In this respect,epitaxial growth is known to require a good match between the latticeparameters and thermal expansion coefficients of the substrate assemblyand the epitaxial layer. By way of example, on bulk GaAs substrate it ispreferred that, the maximum lattice mismatch not exceed about 1%,otherwise stacking defects typically occur in the epitaxial layer. Inone embodiment, techniques can be used that have been developed thatallow higher mismatches between the lattice parameters, while making amultilayer structure with an epitaxial seed layer that is sufficientlythin to be able to match itself to the characteristics of theepitaxially grown material by deformation.

[0011] It has also to be observed that InP as a substrate for themicro-electronics industry is rapidly gaining popularity. Because of itsintrinsic properties, InP and its alloys (InGaAs, AlInAs, InGaP,InGaAsP, InGaAsN, etc.) that can be epitaxially grown thereon withlattice matching, allow transistors to be produced with excellent cutoffand transition frequencies. InP technology is thus the most favorablefor producing very high speed optical transmission networks. Inoptoelectronics, emitters and receivers produced using InP technologycan function within wavelength ranges that are used in opticaltelecommunications. Due to this combination of characteristics, thisgroup of materials can wholly integrate the associated photonicfunctions and electronic functions of control and amplification in theoptoelectronics field. Finally, in the field of microwave amplification,the high power or low noise levels developed by high energy mobility(HEMT) field effect transistors produced using InP technology alsocontributes to the great success of InP technology.

[0012] Currently available substrates formed from InP substrates and thelike are bulk substrates obtained by ingot preparation techniques. Thereare two principal techniques for growth by pulling: liquid encapsulatedCzochralski, LEC, and vertical gradient freezing, VGF, as well as avariety of variations and improvements.

[0013] The production of large, high quality InP crystals, however, istraditionally fraught with difficulties that involve the crystallizationproperties of the material. Low twin crystal creation energy and lowstacking fault energy promote the appearance of defects in thecrystalline structure produced, and the density of these defects hastypically increased with ingot size.

[0014] Incorporating certain impurities into the melt mixture is alsoknown, either to provide N or P type doping or to render the materialsemi-insulating, which is accomplished by compensation, preferably withiron. Substrates are sliced from said ingots along the desiredcrystallographic direction, generally (100) or (111). Subsequentmechanical-chemical polishing produces a finished substrate on whichepitaxial growth can be carried out. Growing iron-compensated InP bypulling, however, has typically been happened by a physical property,namely the extremely low segregation coefficient of iron in InP[K(Fe)=10⁻³]. This causes excessive iron incorporation close to the seedas growth commences, followed by depletion of iron in the melt. An ironconcentration gradient exists from the head to the tail of the ingotthat results in a variation in iron concentration along the ingot. Thevariation in iron concentration can be as high as one order ofmagnitude: for example 10¹⁶ cm⁻³ at one end of the ingot axis and 10¹⁷cm⁻³ at the other end. Compensation of the substrate, and thus itsresistivity, will vary substantially depending on its original positionin the ingot.

[0015] To overcome this problem it is possible to proceed to an aposteriori bulk-substrate compensation. A technique for incorporatingiron by ion implantation would potentially irreversibly damage the InPmaterial.

[0016] It is known that InP can be compensated using a diffusiontechnique. Generally, sealed quartz tube diffusion is employed at a hightemperature (about 900° C.) with a compound that is rich in iron andphosphorus, providing a vapor pressure of several atmospheres. Thepresence of phosphorus prevents desorption of the phosphorus componentof the InP from the substrate surface.

[0017] The thickness of bulk substrates typically imposes very longdiffusion times (typically at least 80 hours (h) for a 600 micrometer(μm) substrate). Thus, this technique is not readily compatible withmass production using bulk substrates.

[0018] Because of the size, brittleness, or cost considerationsmentioned above, or to provide the substrate with a characteristicscompatible for epitaxy, a skilled person may wish to use a SMART-CUT®type technique to transfer a thin layer of InP onto a support. Thistechnique has been carried out for unintentionally doped InP layers, orthose doped with the usual dopants (S, Sn and Zn), or compensated by thepresence of iron (see the article by E. Jalaguier et al in Proc 11^(th)Int Conf InP and Related Materials, pp 26-7 (1999)). In the case ofsemi-insulating InP compensated with iron or another compensatingmaterial, undesirable interactions are observed between the implantedspecies (typically hydrogen) and the complexes present in the materialand involving iron atoms. Thus, improvements in these processes aredesired.

SUMMARY OF THE INVENTION

[0019] The invention relates to a method of producing a productsubstrate, which comprises providing a donor wafer that is substantiallyfree of foreign atomic species; implanting atomic species into the donorwafer to a preselected depth therein to form a weakened zone below abonding face of the donor wafer to define a transfer layer between theweakened zone and the bonding face, the weakened zone being configuredto facilitate detachment of the transfer layer; bonding the donor waferat the bonding face to a support; detaching the transfer layer from thedonor wafer along the weakened zone to obtain a product substrate thatcomprises the support and the transfer layer; and diffusing atomicforeign species into the transfer layer, wherein the foreign species isselected to modify at least one of the electrical or optical propertiesof the transfer layer.

[0020] In a preferred embodiment of the method, atomic species areimplanted into a donor wafer that is substantially free of a preselectedforeign species. Also, in a preferred embodiment, the foreign atomicspecies are diffused into the transfer layer to a depth smaller than thedepth of the implantation. The transfer layer can be thinned after thedetaching, if desired, to remove a portion thereof that is substantiallyfree of the foreign species.

[0021] Additionally, a bonding layer can be formed on one or both of thebonding faces of the donor wafer and the support to improve the strengthof the bonding therebetween. The bonding layer can be configured to forma buried insulator and the product substrate.

[0022] The preferred transfer layer is made of a Group III-Vsemiconductor. Preferably, the foreign atomic species are selected torender the material of the transfer layer semi-insulating once theforeign species are diffused therein. A preferred material for thetransfer layer is indium phosphide, and a preferred foreign speciesincludes one or both of iron or rhodium. Thus, the foreign atomicspecies can comprise a shallow acceptor and a shallow donor. Thepreferred implanted atomic species comprises at least one of hydrogenions or rare gas ions, and the material from which the support is madeis preferably mechanically stronger than the transfer layer.

[0023] Furthermore, an epitaxial layer can be epitaxially grown on thetransfer layer of the substrate after the detachment, and the preferredlattice structure of the epitaxial layer is different than that of thetransfer layer. The preferred thickness of the transfer layer is lessthan about 10 μm, and the preferred method of detaching is by applyingstress to the weakened zone.

[0024] The invention also relates to a donor wafer for transferring atransfer layer to a support, at least one thin crystalline layer thathas a predetermined thickness and comprises a semiconductor materialsuitable for fabricating a substrate for microelectronics, electronics,optoelectronics, or optics when transferred to a support. A foreignatomic species is diffused into the transfer layer to a depth that isless than the predetermined thickness, and the foreign species isselected to modify at least one of the electrical and optical propertiesof the transfer layer of the semiconductor material. The transfer layercan have an exposed bonding surface configured for bonding to thesupport, and the foreign species can be disposed in a region extendingfrom the bonding surface to the depth of the diffusion. Atomic speciescan be implanted adjacent the transfer layer at the thickness thereof tosubstantially limit the transfer layer and to facilitate the cleaning ofthe transfer layer from the remainder of the donor wafer. The preferredmaterials used in this embodiment are those listed above with respect tothe preferred method.

[0025] The present invention thus can provide greater uniformity andcontrollability of the concentration of the diffused foreign species ina controlled location in a produced substrate, and can be obtainedwithout affecting the detaching of the transfer layer from the donorwafer and the formation of the produced substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Other aspects, objects, and advantages of the present inventionwill become apparent from the following detailed description ofpreferred embodiments of the invention, given by way of non-limitingexample and made with reference to the accompanying drawings, in which:

[0027] FIGS. 1A-1E show steps of a method in accordance with a firstembodiment of the invention; and

[0028] FIGS. 2A-2F show steps of a method in accordance with a secondembodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Although studies have demonstrated the favorable role played bythe presence of dopants or impurities in the material on the coalescencekinetics of implanted species prior to cleavage, the Applicant hasdiscovered that iron acts differently, probably by modifying themigration kinetics of hydrogen during implantation then duringannealing. This means that the selection of implantation conditions(dose, energy, temperature) and annealing conditions (duration,temperature) becomes much more difficult. Further, the roughness of thefree face of the transferred layer following detaching is increased,thus increasing the polishing work and producing a material loss whichharms the industrial efficiency and the economics of the method.

[0030] To overcome this, in a first aspect, the invention provides amethod of producing a substrate comprising a transfer crystalline layertransferred from a donor wafer onto a support. The transfer layerincludes one or more foreign species intended to modify its properties.A preferred method comprises the following steps, preferably, insequence:

[0031] implanting atomic species into a zone of the donor wafer that issubstantially free of the foreign species to form a weakened zone belowa bonding face, the weakened zone and the bonding face delimiting atransfer layer to be transferred;

[0032] bonding the donor wafer at the level of its bonding face to asupport;

[0033] applying stresses in order to produce a cleavage in the region ofthe weakened zone to obtain a substrate comprising the support and thetransfer layer; and

[0034] diffusing foreign species into the thickness of the transferlayer prior to implantation or after fracture, suited to modify theproperties of the transfer layer, preferably its electrical or opticalproperties.

[0035] Certain preferred and non-limiting aspects of this method are asfollows:

[0036] the step of diffusing foreign species can be carried out aftercleavage;

[0037] the step of diffusing foreign species can be carried out prior tothe implantation;

[0038] the step of diffusing foreign species can be carried out to adepth that is smaller than the implantation depth;

[0039] the method can include, after cleavage, a thinning step suited toremove the portion of the transferred layer that is depleted in foreignspecies;

[0040] the method can include, prior to bonding, a step of producing abonding layer on the donor wafer and/or on the support;

[0041] the bonding layer can form a buried insulator in the finalsubstrate;

[0042] the material of the donor wafer is preferably a III-Vsemiconductor compound;

[0043] the foreign species can include a species that can render thecompound semi-insulating by diffusion;

[0044] the compound is preferably indium phosphide;

[0045] the foreign species can be selected from the group constituted byiron and rhodium;

[0046] the foreign species can include a combination of a shallowacceptor such as mercury or cadmium and a shallow donor such as titaniumor chromium;

[0047] the implanted species can comprise at least one species selectedfrom hydrogen ions and rare gas ions;

[0048] the support material is preferably selected to be mechanicallystronger than the material of the transfer layer;

[0049] the method can include a subsequent epitaxial growth step carriedout on the transfer layer of the substrate;

[0050] the lattice of the epitaxially grown material can be mismatchedwith the material of the transfer layer.

[0051] In a second aspect, the invention can provide a donor wafercomprising at least one layer of a crystalline material for implementinga method of transferring thin layers of semiconductor material of apredetermined thickness removed from the wafer onto a support forfabricating substrates for microelectronics, optoelectronics or optics.The wafer preferably comprises, on the side of the removal and over adepth that is smaller than said predetermined thickness, at least onediffused foreign species that can modify the properties of the materialof said donor wafer.

[0052] Preferred and non-limiting aspects of said wafer are as follows:

[0053] the material of the wafer can be a III-V semiconductor compound,and the foreign species can be capable of rendering the material of thewafer semi-insulating;

[0054] the III-V semiconductor compound is preferably indium phosphide;

[0055] the foreign species can be selected from the group comprisingiron and rhodium.

[0056] The steps of a first embodiment of the invention are describedbelow using as an example a thin layer from an InP donor wafer 20,transferred to a support or stiffener 10 formed from silicon. First, thefaces to be bonded to the support 10 and the donor wafer 20 are providedwith a bonding layer 11,21 (typically oxide or nitride) to form ahydrophilic surface for molecular bonding (FIG. 1A).

[0057] To this end, the donor wafer 20 and the support 10 preferablyundergo chemical treatment based on hydrofluoric acid to remove thenatural oxide layer. The support 10 is oxidized by thermal oxidation.This technique is particularly suitable for silicon. For InP, however,plasma vapor phase deposition is preferably employed. The bonding layers11,21 are generally about a few hundred nanometers thick.

[0058] Atomic species implantation is then carried out into the donorwafer 20 at the face provided with the bonding layer 21 to form agenerally planar weakened zone 22, which defines a thin layer to betransferred 23 between weakened zone 22 and layer 21 (FIG. 1B). The term“atomic species implantation” as used in the present text means anyintroduction, preferably by bombardment, of atoms or molecules, whichmay or may not be grouped, and which may or may not be ionized. Thisimplantation can be carried out, for example, using an ion beamimplanter or a plasma immersion implanter. Different types of speciescan be implanted, such as H+, H₂ ⁺, or rare gas ions such as He⁺. It isalso possible to carry out co-implantation with an element such asboron.

[0059] Preferably, ionic implantation into the wafer 20 is carried outafter heating the wafer 20. The range of temperatures used differsdepending on the materials of the wafer 20. In the case of InP, thetemperature is preferably in the range between 150° C. to 250° C. Thedose used to implant hydrogen ions into that material is preferably inthe range 10¹⁶ to 5×10¹⁷ H⁺/cm².

[0060] The next step preferably is molecular bonding of the implanteddonor wafer and the support at the bonding layers 21,11 (FIG. 1C). Thisbonding at flat, smooth surfaces in the preferred embodiment. Thesurfaces can be polished using conventional mechanical-chemicalpolishing techniques. In the case of hydrophilic type bonding, it isalso preferable to increase the surface concentration of moleculesterminating in OH that allow bonding. To this end, the donor wafer andsupport can be immersed in a RCA or SCI solution (H₂O:H₂O₂:NH₄OH=5:1:0.2-1). It is then dried at a temperature below 90° C.The donor wafer and support are then assembled at ambient temperatureunder slight pressure, and the assembly is annealed, typically between250° C. and 400° C. Annealing acts to reinforce bonding at the bondinginterface, and also to cause micro-cracks to appear which, oncoalescing, start to fracture and detach the InP film along the plane ofthe weakened zone created by the implanted zone (FIG. 1D). In FIG. 1D,reference number 30 designates the insulating layer substantially formedby the bonded layers 21,11.

[0061] Preferably, the surface 27 of the transfer layer that remainsexposed is then thinned to remove the superficial implanted zone that isrich in atomic species, such as hydrogen atoms. Different techniques canbe used: wet/dry etching and/or mechanical-chemical polishing. A dryetching thinning technique that may prove to be particularly suitable isa spray thinning and smoothing technique.

[0062] To obtain a semi-insulating layer 25, such as with a resistivityof more than about 10⁷ Ohm.cm, by diffusion of iron 24 therein (FIG. 1E)from the transfer layer of InP 23, the assembled structure is placed ina sealed quartz tube at a high temperature (about 900° C.), in a gasmixture composed of iron and phosphorus (preferably FeP₂). The pressureis typically several atmospheres. The diffusion period, which isessentially proportional to the thickness of the InP layer in which thediffusion is to be considered, is estimated to be about ten minutes fora thickness or the order of one micrometer. The preferred FeP₂ gas ispreferably obtained from high purity iron powder and from red phosphorusin a molar ratio of 1:2.

[0063] Exposure to the high temperature employed during this diffusionalso has an annealing function, which endows the InP material with asemi-insulating nature with an iron concentration that is significantlylower than in the case of a non-annealed material (typically from 10¹⁵atoms.cm² instead of 10¹⁷ atoms.cm², as described by R. Fomari et al. in“Conductivity Conversion of Lightly Fe-doped InP Induced by ThermalAnnealing: A Method for Semi-Insulating Material Production”, J ApplPhys 81 (11) 1997, pp 7604-11).

[0064] In a preferred embodiment, the concentration of the diffused ironis at least enough to provide an effective and sufficient compensatingiron in the InP. Additionally, the preferred annealing is carried out atan elevated temperature, typically around 900° C. for several hours, andwith a slow cooling, typically around 0.5 to 1° C./minute.

[0065] It is considered that this effect derives from a large reductionin shallow donors, which would typically be present in a concentrationabout 4×10¹⁵ atoms.cm⁻³. The concentration of shallow donors is related,but not proportionally, to the iron concentration. The reduction of thenecessary concentration of iron allows in this case a very high mobilityof residual free electrons. Further, the annealing treatment produces athermal stability that improves the aptitude of the substrate toimplantation for the fabrication of devices. Because the atomic speciesimplanted into the material of an InP donor layer are present eventhough the material is still depleted in iron, the implantation,coalescence, and cleavage phases can be carried out under the goodconditions, without the perturbation described above caused by the iron.

[0066] In a variation, iron can be diffused from a diffusion source ,that is, such as a solid thin film, rich in iron, assembled onto thefree face of the transferred layer 23. The assembly is exposed to a heattreatment that encourages diffusion. This method protects the surface ofthe transfer layer and substantially reduces and preferably prevents anyphosphorus desorption.

[0067] Treatment of the final surface of the structure comprising thesupport 10, the intermediate insulating layer 30 and the transfer layer25 is preferably carried out by spray projection of neutral atoms, suchas argon, in clusters to obtain an initial planarization and smoothingof the surface by mechanical and/or mechanical-chemical polishing. Thefinal roughness value, measured in terms of standard deviation, is ofthe order of a few Angstroms.

[0068] The substrate can either be delivered as is to the componentindustry destination for epitaxial growth over the transfer layer 25,thus forming a growth seed. The substrate can otherwise be provided withan epitaxially grown layer following the sequence of steps describedabove. The preparation required for epitaxy can include a step ofstabilizing the surface oxide and using tensioactives to provide thesurface with a hydrophilic nature.

[0069] Referring to FIGS. 2A-2F, in a preferred embodiment, iron isdiffused into the donor wafer 20 (FIG. 2A), but in a shallow depth layer25. More precisely, the depth of layer 25 is preferably smaller than thedepth to which the atoms will subsequently be implanted to form theweakened zone (FIG. 2C). FIG. 2B shows the intermediate production ofthe bonding layer 21, and FIG. 2D illustrates the bonding step.

[0070] Migration of the implanted species can result in fracture anddetaching from the donor wafer 20 of a transfer layer 23 comprising thelayer 25 that has received iron diffusion and a layer 26 in which ironis substantially absent (FIG. 2E). Since the migration occurs in a zonein which iron atoms are absent or at least sufficiently rare so assubstantially not to perturb the migration and the resultingcoalescence, the cleavage can occur in a region with favorableconditions.

[0071] This embodiment is advantageous in that it preferably avoids thehigh temperature annealing required to diffuse iron into a multi-layerstructure. Differences between the thermal expansion coefficients aresusceptible of generating very high stresses. By exposing a bulk (noncomposite) substrate to a high temperature for diffusion, expansion ofthe substrate does not generate the shear stresses. Hence, prior to thesurface treatment, the structure illustrated in FIG. 2E is obtained,with a zone 26 of the transfer layer that is substantially free of ironand a zone 25 containing diffused iron, adjacent to the buriedinsulating zone 30. The depth of the implanted zone 22 with respect tothe thickness of the zone 25 is selected so that subsequent thinning cancompletely remove zone 26, and if necessary a small fraction of the zone25, to obtain a final transfer layer 25 that is homogeneously ironcompensated throughout its thickness.

[0072] A number of variations of the invention are possible. Forinstance, the diffused material can be any material incorporated into atransfer layer before or after transfer to the support substrate, tomodify the physical, chemical or electrical properties thereof, andwhich counters migration of the implanted species during theimplantation step. In this respect, although iron is currently the onlyelement used on an industrial scale to render InP semi-insulating,compensation elements with a lower diffusivity than iron—to limitcontamination of other parts of the structure by iron and the risk ofiron depletion—could also be used.

[0073] In this regard, as indicated in the article by A. Näser et al,“Thermal Stability of the Mid-gap Acceptor Rhodium in Indium Phosphide”,Appl Phys Lett, 67, 479-481 (1995), rhodium is known to be a deepacceptor in InP (dual activation energy of 620 milli electron-volts(meV) and 710 meV) that is thermally very stable to diffusion in InP.While rhodium may prove to be problematic in use for bulk InP substratesas it cannot compensate all of their volume, it becomes practical with atransfer layer of transferred InP in accordance with the presentinvention. Typically, according to the study by A. Näser et al citedabove, the dose of rhodium would be about 1×10¹⁷ atoms.cm⁻³ to a depthof 250 nm.

[0074] InP compensation can also be achieved using a combination ofelements, for example a shallow acceptor, such as Hg or Cd, combinedwith a deep acceptor, such as Ti or Cr. Resistivities of 10⁴ to 10⁵ohm.cm are obtained. Mercury and titanium have the advantage of having amuch lower diffusivity than iron and could limit contamination ofneighboring parts of the structure that is produced.

[0075] In conclusion, the present invention can produce a structure thathas:

[0076] a transfer film of InP with diffused Fe;

[0077] an optional amorphous bonding layer (SiO₂, Si₃N₄, etc.); and

[0078] a support, for example monocrystalline, polycrystalline Si, etc.while using a thin film transfer method without perturbation by iron.

[0079] In one embodiment, by selecting non-doped InP, transfer of a thinInP film using a layer transfer method, such as Smart-Cut®, isfacilitated. Further, iron diffusion of InP in a gas source, since it iscarried out at a very high temperature (about 900° C. or more), improveshomogeneity of iron distribution, compensation efficiency(resistivity/iron concentration ratio), and consequently improves themobility of residual free electrons.

[0080] Since the diffusion step is carried out in a thin film of lowthickness, preferably less than about 10 μm, more preferably less thanabout 5 μm, still more preferably less than about 2 μm, and mostpreferably between about 1.5 μm and 0.5 μm, the duration of this step istypically a few minutes, i.e., about two orders of magnitude shorterthan diffusion into a bulk substrate, preferably less than about 10minutes, and most preferably less than about 8 minutes, which takes aneconomically prohibitive length of time for most industrialapplications. In one embodiment, the preferred thickness of the thinfilm in which the diffusion takes places is around 1 μm. The presentmethod is thus compatible with industrial application.

[0081] With regards to size, since the maximum diameter of InP wafers iscurrently 100 mm based on commercially available material, they can betransferred to a larger diameter support. Thus, these partial-substratescan subsequently be used in fabrication facilities for larger standards.As an example, it becomes possible to use certain GaAs technologyequipment for which the standard substrate size: 150 mm with the partialsubstrates.

[0082] Furthermore, compared with a bulk substrate, the support, forexample made of Si, of the structure results in increased strength. Thisadvantage leads to a reduction in losses during transport, manipulationand fabrication of components and circuits.

[0083] Finally, depending on the transition layer employed, theinvention can produce a partial substrate with a compliant character forepitaxy because of the very thin InP layer. This means that epitaxialgrowth of a material with a lattice mismatch of 1% or more and/or with athermal expansion coefficient that differs from that of InP can befacilitated.

[0084] The present invention is applicable to all materials that maycontain foreign elements perturbing coalescence of the implanted speciesnecessary for a layer transfer method such as Smart-Cut®. It is notlimited to the embodiments described and shown herein. Whileillustrative embodiments of the invention are disclosed, it will beappreciated that numerous methods and other embodiments may be devisedby those skilled in the art. Therefore, it will be understood that theappended claims are intended to cover all such modifications andembodiments that come within the spirit and scope of the presentinvention.

What is claimed is:
 1. A method of producing a product substrate, whichcomprises: providing a donor wafer that is substantially free of foreignatomic species; implanting atomic species into the donor wafer to apreselected depth therein to form a weakened zone below a bonding faceof the donor wafer to define a transfer layer between the weakened zoneand the bonding face, the weakened zone being configured to facilitatedetachment of the transfer layer; bonding the donor wafer at the bondingface to a support; detaching the transfer layer from the donor waferalong the weakened zone to obtain a product substrate that comprises thesupport and the transfer layer; and diffusing atomic foreign speciesinto the transfer layer, wherein the foreign species is selected tomodify at least one of the electrical or optical properties of thetransfer layer.
 2. The method of claim 1, wherein foreign atomic speciesis diffused into the transfer layer after detaching the transfer layerfrom the donor wafer.
 3. The method of claim 1, wherein foreign atomicspecies is diffused into the transfer layer prior to implanting theatomic species that form the weakened zone.
 4. The method of claim 3,wherein the foreign species is diffused into the transfer layer to adepth that is smaller than the depth of implantation of the atomicspecies that form the weakened zone.
 5. The method of claim 4, whichfurther comprises thinning the transfer layer after the detaching toremove a portion thereof that is substantially free of the foreignatomic species.
 6. The method of claim 1, which further comprisesproducing a bonding layer on at least one of the bonding face of thedonor wafer or on the support, or on both, to improve bonding strengththerebetween.
 7. The method of claim 6, wherein that the bonding layeris configured to form a buried insulator in the product substrate. 8.The method of claim 1, wherein transfer layer comprises a Group III-Vsemiconductor.
 9. The method of claim 8, wherein the foreign atomicspecies is selected to render the transfer layer to be semi-insulatingby the diffusion of the foreign atomic species therein.
 10. The methodof claim 9, wherein the transfer layer is made of indium phosphide. 11.The method of claim 10, wherein the foreign atomic species comprises atleast one of iron or rhodium.
 12. The method of claim 10, wherein theforeign atomic species comprises a shallow acceptor and a shallow donor.13. The method of claim 1, wherein the implanted atomic species thatforms the weakened zone comprises at least one of hydrogen ions and raregas ions.
 14. The method of claim 1, wherein the support material ismechanically stronger than the transfer layer.
 15. The method of claim1, which further comprises epitaxially growing an epitaxial layer on thetransfer layer of the substrate after the detaching.
 16. The method ofclaim 15, wherein the epitaxial layer has a lattice structure that isdifferent than that of the transfer layer.
 17. The method of claim 1,wherein the transfer layer has a thickness of less than about 10 μm. 18.The method of claim 1, wherein the detaching of the donor wafer isachieved by applying stress to the weakened zone.
 19. In a method forproducing a product substrate by implanting atomic species into a donorwafer to a preselected depth therein to form a weakened zone below abonding face of the donor wafer to define a transfer layer between theweakened zone and the bonding face, the weakened zone being configuredto facilitate detachment of the transfer layer; bonding the donor waferat the bonding face to a support; and detaching the transfer layer fromthe donor wafer along the weakened zone to obtain a product substratethat comprises the support and the transfer layer; the improvement whichcomprises diffusing atomic foreign species into the transfer layer priorto or after detaching, wherein the foreign species is selected to modifyat least one of the electrical or optical properties of the transferlayer.
 20. A donor wafer for transferring a layer therefrom to asupport, the donor wafer comprising: at least one transfer layer of acrystalline material that has a predetermined thickness and comprises asemiconductor material suitable for fabricating a substrate formicroelectronics, optoelectronics or optics when transferred to thesupport; and a foreign species diffused into the transfer layer to adepth that is less than the predetermined thickness of the transferlayer; wherein the foreign species is selected to modify at least one ofthe electrical and optical properties of the transfer layersemiconductor material.
 21. The donor wafer of claim 20, wherein thetransfer layer has an exposed bonding surface configured for bonding tothe support, and the foreign atomic species is disposed from the bondingsurface to the depth.
 22. The donor wafer of claim 20, wherein theatomic species that are implanted at the thickness substantially delimitthe transfer layer and facilitate detachment of the transfer film fromthe donor wafer.
 23. The donor wafer of claim 20, wherein thesemiconductor material is a Group III-V semiconductor, and the foreignatomic species renders the transfer layer to be semi-insulating.
 24. Thedonor wafer of claim 23, wherein the semiconductor material is indiumphosphide.
 25. The donor wafer of claim 24, wherein the foreign atomicspecies comprises at least one of iron or rhodium.